The invention relates to a novel molding material based on polyisocyanato-isocyanurates, polyols and flameproofing and fireproofing agents, as well as optionally polyisocyanates, fillers and promoters, which is particularly suitable for use as construction and repair material and especially from the quick processing and the fire protection standpoint leads to excellent products.
Duroplastic compounds and foams of polyurethane with isocyanate and isocyanurate components, epoxy resins (EPO resins), phenolic resins and novolacs are known, which contain flame-inhibiting additives and which constitute difficultly or nonflammable materials. In order to improve the fire resistance and achieve a low smoke density and toxicity, a large number of different formulations has been proposed. As flame-inhibiting additives are inter alia proposed Al.sub.2 O.sub.3 .times.H.sub.2 O, organic and inorganic phosphates or phosphonates, borates, silicates, chlorinated paraffins, halogen compounds, heavy metal salts, elementary phosphorus, polyphosphates and antimony trioxide. Reference is made in exemplified manner in this connection to U.S. Pat. Nos. 4,126,473 and 4,147,690, European Pat. No. 69 975 and DE-OS No. 31 05 047. A survey of the prior art appears in Becker-Braun, Kunststoffhandbuch, vol. 7, Polyurethanes, second edition, 1983, Hanser-Verlag; J. Troitzsch, Brandverhalten von Kunststoffen, Grundlagen etc., Carl Hanser-Verlag, 1982; and Polymerwerkstoffe, vol. 2, Technologie 1, H. Batzer et al., Georg Thieme Verlag, Stuttgart, 1984.
With individual additions or combinations of such flame-inhibiting additives in part very satisfactory results are obtained. In view of the great increase in the use of plastics, nowadays extreme demands regarding fire protection are made in the field of the conveyance of passengers through a number of standards and specifications, particularly with respect to the aircraft and car industry, as well as in ships, trains and in the building industry. This is documented in various national and international test standards, such as DIN 75200, DIN 4102, DV 899/35 (Germany), FAR 25.853, MVSS 25.853 (USA), AFNOR P 92-507 (France), etc. As it is to be expected that these standards will be made even stricter in future and apart from non-flammability, special importance will be attached to the density and toxicity of the smoke gas in the case of charring and/or fires, in 1979 the Airbus consortium drafted its own stricter standards, ATS 1000.001 and made it available to the relevant branches of industry. In the case of an estimated aircraft life of at least 15 years, this standard already takes account of future technical developments and demands (ct. TU 21, 1980, No. 2, February, pp 79-82 and "Die chemische Produktion", 1983, pp 50-53).
The one- and two-component molding materials presently used in the aircraft industry do not yet meet the requirements of ATS 1000.001.
In the aircraft industry such molding materials are e.g. used for producing reinforcements and mountings (inserts), internal coverings (e.g. side walls and partitions, as well as roof coverings), floors, insulating and covering plates, as well as molded parts. Particular preference is given to the use of so-called prepreg components (sandwich honeycomb constructions), which are constituted by phenolic resin honeycombs coated with multilayer resin mats (trade name Nomex). The resin mats (prepegs) comprise E-glass fabrics, which are impregnated with resins based on phenol/formaldehyde, unsaturated polyesters, EPO and polyimides. With a view to increasing stability and saving edging profiles, an edge filling mass is often pressed into the honeycombs on the edges of the sandwich components.
A molding material able to satisfy demands in the foreseeable future must cure without shrinkage and lead to a construction material with a low density of approximately 0.2 to 0.8 g/cm.sup.3, which ensures high bending and compression strengths both at ambient temperature and under continuous thermal influences up to 80.degree. or 130.degree. C. To this must be added the demands in connection with fire and/or charring, namely non-flammability, no dripping, insignificant smoke gas emission and substantially non-toxic pyrolysis gas evolution. For special uses (e.g. fire protection walls in the transportation area of aircraft) higher thermal stability would also be necessary, i.e. the material must be able to withstand e.g. a temperature of 1000.degree. to 1200.degree. C. for 10 minutes. With regards to the conventional composite system in which such molding materials are used, there must be an optimum connection or adhesion with the materials forming the basis of such composite systems, such as polymers, polycondensates or polyaddition compounds (e.g. unsaturated polyesters, EPO resins, phenolic resins, polyimide or polyurethane). It is necessary or at least desirable to also have an optimum connection or adhesion to metals and materials such as glass and carbon fibres.
The formulations and systems known from the prior art, which are described in numerous patent specifications and applications, only partly fulfil certain of the above requirements or combinations of partial ranges thereof.
Thus, European Patent application No. 157 1433 describes fire-inhibiting sealing compounds, which comprise melamines and a number of fillers which, apart from other inadequacies, have densities of 0.7 to 1.0 g/cm.sup.3.
DE-OS No. 35 19 581 describes ablation coatings of amine-cured EPO and polysulphide resin mixtures with pre-ox-carbon fibres as a reinforcement which, although resistant to high temperatures, have densities well above 1.0 g/cm.sup.3.
DE-OS No. 27 14 006, DE-OS No. 27 13 984 and DE-OS No. 27 40 504 describe molding materials comprising polyisocyanate and hollow spheres. These are cured through access of atmospheric humidity and optionally after addition of water. Preferably, shortly prior to processing phosphoric acid and/or phosphates or their aqueous solutions or alkali silicate solutions are added. The molding materials described in these patent applications only have a relatively low compression strength in the cured state and are only storage-stable in the form of premixes constituted by polyisocyanate and hollow spheres. However, they are not stable as moisture-curing one-component materials and therefore do not have the processing advantages linked with the latter. Tests have revealed that e.g. mixtures of hollow spheres with 2% polyisocyanates do not give stable materials. Materials produced according to the process of claim 2 of DE-OS No. 27 14 006 (plates with a thickness of 5 to 10 mm) were unable to withstand a temperature of 1080.degree. C. for one minute.
Therefore the problem existed to avoid the above described disadvantages of known molding materials and to obtain improvements to the characteristics, particularly in the fire protection field. Especially there existed the problem of providing molding materials which, apart from the aforementioned characteristics, in the cured state have high compression strength characteristics not only at ambient temperature but also at elevated temperatures up to 80.degree. C. (decrease of compression strength at 80.degree. C. in comparison to room temperature of less than 40%), meet very high demands regarding flammability, smoke gas density and the evolution of toxic pyrolysis gases in the case of charring and/or fire, do not afterflame, do not drip, are resistant to water, hydraulic fluid and kerosene, provide excellent binding to any standard prepreg materials, metals and fibrous materials and cure in shrinkage-free manner.
For the solution of these problems a one-component molding material based on polyisocyanato-isocyanurates and flameproofing and fireproofing agents as well as optionally polyisocyanates, fillers and promoters has been proposed in prior application Ser. No. 24026 filed on Mar. 10, 1987 comprising:
A. 40 to 80% by weight of the isocyanurate of 1,6-hexamethylene diisocyanate with a NCO content of 18 to 24% by weight, PA0 B. 0 to 20% by weight of crude MDI and/or prepolymer of polyol and crude MDI and/or isophorone diisocyanate optionally in combination with dimerized triazine of TDI, copolymerized triazine of TDI and HDI and/or naphthalene diisocyanate, PA0 C. 5 to 20% by weight of a mixture of: PA0 D. 0 to 50% by weight of filler and PA0 E. 0 to 5% by weight promoter. PA0 A. 5 to 40% by weight of branched polyols having an OH content of 2 to 22% by weight, PA0 B. 20 to 40% by weight of the isocyanurate of 1,6-hexamethylene diisocyanate, PA0 C. 0 to 20% by weight of crude MDI and/or prepolymer of polyol and crude MDI and/or isophorone diisocyanate (IPDI) optionally in combination with dimerized triazine of TDI and/or copolymerized triazine of TDI and HDI and/or naphthalene diisocyanate, PA0 D. 5 to 20% by weight of a mixture of: PA0 E. 0 to 50% by weight filler and PA0 F. 0 to 5% by weight promoter.
a. 50 to 100% by weight of secondary ammonium phosphate with the proviso that the amount of secondary ammonium phosphate is 80 to 100% by weight if component C is only present in an amount of 5 to 10% by weight, PA1 b. 0 to 20% by weight of primary ammonium phosphate, PA1 c. 0 to 20% by weight of zeolite and/or crystalline alkali silicate, PA1 d. 0 to 20% by weight of finely divided silica, PA1 e. 0 to 20% by weight of Ca.sub.3 (PO.sub.4).sub.2, PA1 f. 0 to 20% by weight azodicarbonamide, PA1 g. 0 to 20% by weight calcined calcium oxide, PA1 a. 50 to 100% by weight of secondary ammonium phosphate, PA1 b. 0 to 50% by weight of primary ammonium phosphate, PA1 c. 0 to 30% by weight azodicarbonamide, PA1 d. 0 to 20% by weight zeolite and/or ground alkali silicate, PA1 e. 0 to 10% by weight finely divided silica, PA1 f. 0 to 10% by weight calcium orthophosphate and PA1 g. 0 to 20% by weight calcined calcium oxide, PA1 1. 40 to 80% by weight component A, PA1 2. 10 to 20% by weight component D, PA1 3. 0 to 50% by weight component E and PA1 4. 0 to 5% by weight component F PA1 1. 40 to 80% by weight component B, PA1 2. 0 to 20% by weight component C, PA1 3. 5 to 20% by weight component D, PA1 4. 0 to 50% by weight component E and PA1 5. 0 to 5% by weight component F,
After cold shaping, the curing of this molding material takes place by ramming, rolling, pressing, extruding, shaking in, blowing in, etc. at ambient or elevated temperature through the action of atmospheric humidity or water vapour. At ambient temperature curing takes place within about 7 dauys or within a single day when adding about 1 to 3% by weight of the above mentioned promoters. However, preferably curing takes place at 110.degree. to 200.degree. C. (e.g. 130.degree. C.) without promoter in about 0.5 to 3 hours. Generally there is a not inconsiderable aftercuring, so that the initially obtained compression strength, e.g. after 4 weeks, can increase by about 20 to 30% and even up to 50%. When curing this molding material, the expert will obviously take account of the molding geometry and thermal conductivity and will choose the necessary curing time accordingly (cf. e.g. DE-OS No. 27 14 006, p 23). Otherwise curing takes place at usual pressures, e.g. atmospheric pressure (pressures of about 0.5 to 50 bar normally being used).
If the relative atmospheric humidity during curing is below about 40%, it is advantageous to add water in concentrations of 1 to 10% by weight, there being no need to define the water quantity. Water can be replaced by aqueous basis, such as e.g. caustic soda and caustic potash solution, or alkaline-reacting compounds, such as sodium or potassium silicates in the form of their aqueous solutions. Ammonium phosphate solutions are also very suitable. Generally 0.5 to 5N solutions are used.
Though the molding material according to this prior patent application completely fulfills the above outlined requirements, it has turned out that in practice it is often desirable to have a molding material which can be used at ambient temperature and permits a quick or quicker processing without using presses or autoclaves. On the one hand curing times of about 7 days or one day when adding promoters (see above) are often not acceptable and on the other hand it is often not possible or at least not desirable to apply temperatures in the above mentioned range of about 110.degree. to 200.degree. C. This is especially true for repairs and particularly for repairs to be carried out in situ which because of the minor influence of the repair material on the overall properties of the repaired part (e.g. volumetric weight) do not to the same extent require the fulfillment and achievement of all of the above mentioned optimum characteristics of the molding material.